The present invention relates to a sewing machine for automatic thread taking-up operation. More specifically, this invention relates to a sewing machine that can automatically take up a needle thread using a thread take-up prior to any sewing operation.
Currently proposed sewing machines can simplify the thread taking-up operation of a needle thread with a thread take-up (hereafter referred to as thread taking-up operation) prior to sewing operation. For example, in sewing machines disclosed in Japan Published Examined Utility Model Application No. S56-27900 and U.S. Pat. No. 3,561,002, a thread take-up is surrounded with a cover provided with a slit. When an operator guides a needle thread along the slit, the needle thread is put on an end of the thread take-up. Subsequently, the thread take-up swings up and the needle thread is caught by the end of the thread take-up. The needle thread is thus taken up. Although the thread take-up has to be in a lower position in these sewing machines, the thread take-up is generally raised up together with the needle bar when the sewing machine is stopped. Therefore, the operator has to lower the thread take-up before guiding the needle thread along the slit.
Japan Published Unexamined Patent Application No. S47-19948 and Japan Published Examined Utility Model Application No. S63-228 propose sewing machines that can automatically perform the thread taking-up operation without lowering the raised thread take-up in advance. In these prior art devices, thread positioning members for stringing a needle thread are provided in the moving area of the thread take-up. The needle thread is not slackened when the thread take-up swings down and pushes away the needle thread. An operator hangs the needle thread on the thread positioning members such that the needle thread is strung with appropriate tension and then swing the thread take-up up and down.
In a general sewing machine, however, the needle thread must be caught by both a thread taking-up member and a thread take-up in a prescribed order. This is a troublesome operation. In addition, the needle thread has to be taken up by the thread taking-up member and the thread take-up with suitable tensile strength such that uneven stitches are prevented at the beginning of the sewing operation.
In prior-art sewing machines, the operator must put the needle thread on the thread taking-up member. Furthermore, some operations are required for the thread taking-up operation. For example, the thread take-up must be lowered, the needle thread must be securely held by the thread positioning member, and so on. Thus, the thread taking-up operation cannot be automatically executed to the full extent desirable and complicated operations for preparing the needle thread are necessary.
Wherefore, an object of this invention is to provide a sewing machine for automatically taking-up a needle thread with a thread take-up and a thread taking-up member.
Other objects and benefits of the invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.